Factor completely. $640-10x^2=$
Answer: First, we take a common factor of $10$. $640-10x^2=10(64-x^2)$ Now, let's factor $64-x^2$. Both $64$ and $x^2$ are perfect squares, since $64=({8})^2$ and $x^2=({x})^2$. $64-x^2 = ({8})^2-({x})^2$ So we can use the difference of squares pattern to factor. ${a}^2 - {b}^2 =({a}+{b})({a}-{b})$ In this case, ${a}={8}$ and ${b}={x}$ : $({8})^2 - ({x})^2 =({8}+{x})({8}-{x})$ $\begin{aligned} 640-10x^2&=10(64-x^2) \\\\ &=10(8+x)(8-x) \end{aligned}$ In conclusion, the complete factorization is $10(8+x)(8-x)$ Remember that you can always check your factorization by expanding it.